Petefts



(No Model.)

J. T. DAVIS.

VAGUUM PUMP.

Patented Oct. 20, 1885.

WITNESSES 2 INVENTOR BY ATTORNEY N PETERS, Phmo-Lnm m her, WzshvngtorL D, 2v

Fries.

PATENT JOHN T. DAVIS, OF NEW YORK, N. Y.

VACUUM-PUMP.

S PECIFICATION forming part of Letters Patent No. 328,469, dated October 20, 1885.

Application filed January 10, 1885. Serial No. 152,443. (No model.)

To all whom it may concern.-

Be it known that I, JNo. 'l. DAVIS, a citizen of the United States, and a resident of New York, in the county of New York, and State of New York, have invented certain new and useful Improvements in Vacuum-Pumps, Air- Oompressors, and Similar Machines, of which the following is a specification.

Of the drawings, Figure 1 is a horizontal section of apump, showing piston,valves, and connections. Fig. 2 is a front end view of the same with a portion removed, showing the interior.

The same letters refer to the same parts throughout.

The object of my invention is to so improve the vacuum-pump as to make it capable of producing and sustaining a more nearly perfect vacuum than has been attained heretofore. For this purpose I make the outletvalve as large as the piston that {is covering the Whole end of the cylinder, and make it movable in the same direction as the motion of the approaching piston, which condenses proaching piston by making actual mechanical contact with the valve has thereby expelled the last particle of the vapor, leaving no clearance whatever. Thus the piston and valve form a positive close joint by the contact of their two faces, which remains until the piston, moving upon its return -stroke, permits the valve to reseat itself upon the end of the cylinder. In the inner face of this discharge-valve I arrange an inlet-valve that follows the stroke of the piston as it recedes, making sufficient opening to admit the vapor to the cylinder, and remaining open until the piston, having reached the opposite end of the cylinder, starts upon another forward stroke, when the inlet valve immediately closes. By this double-valve system I secure a device that will handle vapors of any degree of tension.

Figure 1 is a longitudinal section, and Fig. 2 an end View, partly in section, of my invention.

To each end of a cylinder, A, is secured, by means of suitable flanges and bolts, a cylindrical shell, B, which covers the exhaustvalve C, and is provided with a nozzle, b, for

making connection with the discharge-pipe. To the outside of the shell B is secured, by similar flanges and bolts, the bonnet D, covering the inlet-valve E, and also provided with a nozzle, (1, suitable for making connection with the vacuunrchamber. The dischargevalve 0 has a ring or cylindrical portion, 0, which extends into the bonnet D, that covers the inlet-valve E, and is fitted into said bonnet by a joint packed, as at d, with any suitable material which will permit the proper motion to the valve 0 and at the same time prevent any communication between the bonnet D or vacuum-chamber and shell B or discharge-chamber, except through the valves 0 E and cylinder A.

In the cylinder A is a piston, F, the rod f of which passes through one of the inlet-valves E and its bonnet D, and is packed at e and d by means of stuffing-boxes and gland, in the usual manner. The packing of the inlet-valve at e steadies that valve in line and provides friction on the rod f, which assists in operating the valve. While the inlet-valve E, at the opposite end of the cylinder, is kept in position by two guide-rods, e e, passing through the piston F and free to slide therein. The inlet-valves E are both secured to the guiderods e,which also pass freely throughaguide, 0, provided in the cylindrical part c of the outlet-valve O. The function of these guiderods 0 is not only to support and align the valves E during their motion, but also to insure that motion by means of friction provided where the rods e pass through the piston F, and also to keep the valves E E at their proper distance apart, causing one to close as the other opens, and vice versa, with each change of motion of the piston F.

The piston F is constructed in two parts, with an annular space, f, between them, in which is fitted a packing, f, of leather, canvas, or other suitable material, so as to secure a perfectly vapor-tight joint, the space f being left within the packing f to admit a lubricating substance-as water or oilwhich, permeating the leather packing, becomes effective upon the inner surface of the cylinder A. An oil-way or limber, f, is also provided in the piston-rod F and the hub of the piston, by means of which the lubricating fluid may be introduced, as required,while in operation, without affecting the vacuum, as would necessarily be the caseif oiled through the cylinder in the usual manner. I An elastic-ring packing, f, is provided in 5 the cylinder F, and, surrounding each of the guide-rods e, performs the double function of making an impervious joint, and also supplying the requisite friction to operate the valves, as described.

The faces of the piston and valves and their seats are cushioned with a sheet of rubber, f or other suitable material, for the purpose of both deadening the blow and perfecting the contact when they come together, as described.

The exhaust-valves Care also provided with springs c", which assist the back pressure of the discharge-chamber in closing the valve as January, A. D. 1885.

' JNO. T. DAVIS.

Witnesses:

BENJ. '1. RHOADS, J J. H. OHEsLEY. 

